Restless leg syndrome in spinal cord injury: case report

CASE DESCRIPTION

Restless leg syndrome (RLS) is a condition infrequently reported in spinal cord injury that causes an uncomfortable sensation in the legs and an urge to move them. We report a case involving a 63-year-old man with incomplete paraplegia with an onset of RLS four years post injury.

FINDINGS

Based upon history, pramipexole was prescribed for the presumptive diagnosis of RLS, with good effect. Initial workup revealed an anemia (hemoglobin of 9.3 gram/deciliter (g/dl)) and iron deficiency (ferritin of 10 microgram/liter (μg/L)), necessitating further evaluation.

CONCLUSION

Due to the complexities in diagnosing RLS in patients with SCI, it is important to be cognizant of symptoms and to consider this diagnosis to initiate the appropriate work-up for an etiology, of which iron deficiency anemia is common.

Transient alteration of consciousness in spinal cord injury secondary to Baclofen use: a case report

INTRODUCTION

Oral baclofen is commonly used for spasticity management, especially with neurogenic bladder in spinal cord injury (SCI). A less common side effect of baclofen is transient alterations of consciousness, which can easily be confused for altered mental status secondary to orthostatic hypotension in SCI.

CASE PRESENTATION

A 43-year-old man with an acute SCI secondary to an aortic dissection was found to have episodes of confusion after titrating oral baclofen from 5 mg three times per day to 10 mg three times per day at an acute rehabilitation facility. Orthostatic hypotension was initially suspected as the cause of transient alterations of consciousness; however, he was never found to be hypotensive during these episodes. His confusion resolved several days after discontinuation of baclofen.

DISCUSSION

Although, confusion and lightheadedness in SCI are commonly caused by orthostatic hypotension, it is important for physicians to be cognizant of baclofen's side effects, which increase in the setting of acute kidney injury (AKI). If an adverse effect is suspected, baclofen should be tapered while remaining observant for signs of baclofen withdrawal, which can be life-threatening. This case report is a reminder for clinicians to be aware of the uncommon adverse effects of baclofen when initiating therapy in SCI, especially in patients with AKI and neurogenic bladders.

Duplex ultrasound surveillance for deep vein thrombosis after acute traumatic spinal cord injury at rehabilitation admission

Context/objective: To determine the prevalence of deep vein thrombosis (DVT) detected through routine duplex screening and factors associated with DVT in spinal cord injury (SCI) patients on admission to rehabilitation.Design: Retrospective chart review of medical records.Setting: Acute inpatient rehabilitation.Participants: One hundred and eighty-nine individuals admitted to rehabilitation within 2 weeks of initial traumatic SCI who underwent routine surveillance with duplex scan for DVT.Interventions: Duplex scan of lower extremities.Outcome measures: The dependent variable was positive duplex screening for either any DVT (distal and/or proximal) or proximal DVT.Results: Of the 189 patients, 31 patients (16.4%) had a positive scan for any (proximal and/or distal) DVT, with 9 (4.8%) positive for a proximal DVT and 22 (11.6%) positive for isolated distal DVT. Of those with isolated distal DVT, 31.8% later developed propagation with either proximal DVTs or pulmonary embolism (mean = 22 days). Factors significantly associated with positive duplex scans for any (proximal and/or distal) DVT include more severe neurological injury (AIS A, B or C versus AIS D: χ² = 7.1791, df = 1, P = 0.007) and older age (age ≥50 years old: χ² = 14.9410, df = 1, P = 0.000).Conclusion: In acute traumatic SCI, older age and more severe neurological impairment (AIS A, B, and C) are independent risk factors for positive duplex screening for any (proximal and/or distal) DVT detected on rehabilitation admission. Individuals with an acute distal DVT have a high likelihood for future thrombus progression. Routine surveillance for these patients may be warranted.

Studying excited states of proteins by NMR spectroscopy

Protein structure is inherently dynamic, with function often predicated on excursions from low to higher energy conformations. For example, X-ray studies of a cavity mutant of T4 lysozyme, L99A, show that the cavity is sterically inaccessible to ligand, yet the protein is able to bind substituted benzenes rapidly. We have used novel relaxation dispersion NMR techniques to kinetically and thermodynamically characterize a transition between a highly populated (97%, 25 degrees C) ground state conformation and an excited state that is 2.0 kcal mol(-1) higher in free energy. A temperature-dependent study of the rates of interconversion between ground and excited states allows the separation of the free energy change into enthalpic (Delta H = 7.1 kcal mol(-1)) and entropic (T Delta S = 5.1 kcal mol(-1), 25 degrees C) components. The residues involved cluster about the cavity, providing evidence that the excited state facilitates ligand entry.

Probing slow time scale dynamics at methyl-containing side chains in proteins by relaxation dispersion NMR measurements: application to methionine residues in a cavity mutant of T4 lysozyme

A relaxation dispersion-based NMR experiment is presented for the measurement and quantitation of micros-ms dynamic processes at methyl side-chain positions in proteins. The experiment measures the exchange contribution to the 13C line widths of methyl groups using a constant-time CPMG scheme. The effects of cross-correlated spin relaxation between dipole-dipole and dipole-CSA interactions as well as the effects of scalar coupling responsible for mixing of magnetization modes during the course of the experiment have been investigated in detail both theoretically and through simulations. It is shown that the complex relaxation properties of the methyl spin system do not complicate extraction of accurate exchange parameters as long as care is taken to ensure that appropriate magnetization modes are interchanged in the middle of the constant-time CPMG period. An application involving the measurement of relaxation dispersion profiles of methionine residues in a Leu99Ala substitution of T4 lysozyme is presented. All of the methionine residues are sensitive to an exchange event with a rate on the order of 1200 s(-1) at 20 degrees C that may be linked to a process in which hydrophobic ligands are able to rapidly bind to the cavity that is present in this mutant.

Measurement of slow (micros-ms) time scale dynamics in protein side chains by (15)N relaxation dispersion NMR spectroscopy: application to Asn and Gln residues in a cavity mutant of T4 lysozyme

A new NMR experiment is presented for the measurement of micros-ms time scale dynamics of Asn and Gln side chains in proteins. Exchange contributions to the (15)N line widths of side chain residues are determined via a relaxation dispersion experiment in which the effective nitrogen transverse relaxation rate is measured as a function of the number of refocusing pulses in constant-time, variable spacing CPMG intervals. The evolution of magnetization from scalar couplings and dipole-dipole cross-correlations, which has limited studies of exchange in multi-spin systems in the past, does not affect the extraction of accurate exchange parameters from relaxation profiles of NH(2) groups obtained in the present experiment. The utility of the method is demonstrated with an application to a Leu --> Ala cavity mutant of T4 lysozyme, L99A. It is shown that many of the side chain amide groups of Asn and Gln residues in the C-terminal domain of the protein are affected by a chemical exchange process which may be important in facilitating the rapid binding of hydrophobic ligands to the cavity.

Flexibility and ligand exchange in a buried cavity mutant of T4 lysozyme studied by multinuclear NMR

The Leu99-->Ala mutant of T4 lysozyme contains a large internal cavity in the core of its C-terminal domain that is capable of reversibly binding small hydrophobic compounds. Although the cavity is completely buried, molecules such as benzene or xenon can exchange rapidly in and out. The dynamics of the unliganded protein have been compared to the wild-type protein by measuring the NMR spin relaxation rates of backbone amide and side chain methyl nuclei. Many residues surrounding the cavity were found to be affected by a chemical exchange process with a rate of 1500 +/- 200 s(-1), which is quenched upon addition of saturating amounts of the ligand xenon. The relationship between the structure, dynamics, and energetics of the T4 lysozyme mutant is discussed.